Re: Substrates

I use a heavy clay soil with a natural pH of 7.8 to 8.0. I cut it 50% 
with sand before it goes into the aquarium. This results in a pH of from 
7.8 to 8.2 for about a year after the tank setup (our water in Winnipeg 
has a pH of approximately 7.6 to 7.8). This has never been a problem for 
any of the plants that I grow. After a while the pH will drop to around 
7.2 to 7.4 with the set up that I have. The hardness of the tapwater is 
around 80 ppm (about 4 to 5 dH) ... the hardness in the tank is about 150 
ppm (about 8 dH) so there is some leakage of base cations from the 
sediment. Again, this has never been a problem for my plants.

IMHO, when you use a soil substrate you have to be prepared to 
experiment because soils are almost infinitely variable so your mileage 
may vary depending on what you have available. Ideally, a fertile silt 
loam should be used, though again, others have produced excellent results 
with a highly organic substrate. I have also had excellent results using 
lake sediments ... in this case the best strategy is to dredge them from 
just beyond a luxuriant macrophyte bed ... I used to keep a large pail of 
this muck, covered with water and stored in the fridge. Parasites were 
never a problem and neither were nematodes ... I think these kind of 
scare tactics are spread by operators who want to ensure that aquarists 
are too frightened to use native wildlife and materials. In actual fact, 
there are many species of plants just outside your door which are 
beautiful and entirely suitable for use in your aquarium (as well as 
being free). As someone who has spent years fooling around with aquatic 
plants in the lab I would urge people to try new things, try different 
things, experiment, have fun, and above all dont listen to what anyone in 
an aquarium store has to tell you. (Of course if you want a show tank in 
your living room you might want to be a little more cautious in the name 
of harmony with your partner(s)).

Dave Huebert.